Go two sizes thicker wire than you think.
Put a decent reg alongside of battery. and you'll get the best results.
ALso stick another couple of panels extra up there,
then you'll get much betterer results in your battery charging in ALL weathers.

Make it 8.

Already had the 6 but problem putting it to red arc reg as holes to put panel wire in are about 3mm would it be better to get a Dc to DC charger? 

Burgo

I use the tradies solar wiring they use on houses.

Any industrial electrical supplier will sell by the mtr. I buy the heavier of the two.
And with multiple panels. wire one to next. to next. etc. till junc box,
then the one wire goes down through roof of van to Reg/Batt's

I use a 2 to 1, or 4 to one gold block for most wiring to van input.
ANy size wiring in. and one wire to suit out. Can make that suitable to carry the current from/to.

Then 60a dual trip and fuses to all batterys.
I want it to blow BEFORE the 100a is reached thank you.
Less chance of damage to things.
My Trips and 30a Regulator take 8mm wire comfortable.

I am not an electrician, so this is a layman type answer

My answer is that YES it is better to have the regulator near the battery

Concerning portable panels, you may have to buy a second regulator
My explanation is that during my own research, the portable panels I looked at, had the regulator glued onto the back of the solar panel
In my opinion, so I could therefore be wrong.
The attempt removal of the regulator from a portable solar panel, will probable result in damage to the solar panel
If you put a second regulator near the battery/s, then you will have to by-pass the original regulator glued onto the portable panel

On the panels for the roof either the regulator was not available from the purchaser, or if it was, it was not glued onto the panel

That was a while ago, so things may have changed by now

Hope that this info is helpful to you